Vacuum resistance-furnace.



A. 0. APPELBERG. VACUUM RESISTANCE PURNAGE.

APPLICATION FILED JULY 2, 19

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A. '0. APPELBBRG.

VACUUM RESISTANCE PURNAGE.

APPLIOA'TION FILED JULY 2, 1000.

953,774e Patented Apr. 5, 1010.

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UNITED sfrafrns PATENT emmen.v

AXEL o. APPELBEBG,

OF SCHENECTAY, NEW YORK, ASSIGNOB. TO GENERAL ELECTRIC; COMP-ANY, ACORPORATION 0F YORK.

VACUUM RESISTANCE-runnen.

speciaeauon of Lettera Patent. i Iatenfted. Apr., 5, 1910. Applicationfiled July 2, 1906. Serial No. $24,391.

To all whom it may concern:

Beit known that I, AXEL 0. A PPEIBERG, a subject of the King of Sweden,residing at Schenectady, county. of Schenectady, State -of New York,have -'invented certain new' and useful Improvements in VacuumResistance-Furnaces, of .which the following is aspecification.' v

This invention relatesto an improvement in electric furnaces andparticularly to means whereby a temperature may be produced approachingthat at which some o the so-called high fusing metalsdisintegrate vor vaorize.' f

'ghe furnace may be used for the fusion or treatment of the morerefractory metals and compounds, and includes 1neansfor protecting thecharge under treatment from oxidation or other change which might result`from contact with air or other atmosphere at the high temperature oftreatment.

My improved furnace is of the resistance type and is provided with aresistance con-V fication, in which- Figure 1 vis a perspective view ofone type.4

of furnace with certain of the parts shown in sectiongyFig. 2 is a lanview taken on the line 1--1 of Fi l; gig.. 3 is a -representation of thecrucib e to be heated and of the resistance conductors Vand thesurrounding refractory shield; Fig. t is a detail illustrating thcconnection between a resistance conductor and the metal block by whichit is supported; and Fig. 5 is a sectional eleva# tion o a modified typeof furnace in which the resistance heater 1s tubular 1n form.

rlhe furnace shown 1n Fig. 1 com rises an air tight metal chamber 1fitted wit a cover vbrass tubes t an .from by mica bushings 9, with theexception lhave hereinafter described the cover to near the bottom ofthe chamber and is then bent in a circular form and passesnpward and outagain through the cover. This tube is insulated from the cover andserves to connect the resistance members of the furnace with one side ofan electrical circuit. A similar tube 5 is arranged in circular formnear the` top of the evacuated chamber to 'support the upper ends oftheheatingA members.` vThese heating members 6V conslst of metal rodsproduced as hereinafter described, and clamped at their endsin blocks 7of the same material, vthe latter being secured to iron clamps 8 bysuitable clips. The clam s 8 are mounted on the 5 and are insulatedthere.

of the clamps 10 and 11 which connect with the end conductors of thegroup; these are -mounted directly on the brass rods' and therebyestablish a connection forv current from the source of pcwerthrgugh thecup of rods in series. They may convenientlyv be made of copper.

Then the heatin conductors are made oi tungsten they maye pressed to thedesired form from finely powdered tungsten, but for convenience inmanufacture it is some- 'times desirable to add a small quantity ofbinding material to the tungsten powder and then squirt or 'mold themixture into rods and blocks necessary for the construction of thefurnace. A 56% glucose solution is a suitable binder and may be addedtol-the tungsten' powder in theproportion of about 5 yparts by weight.,When glucoseis used I prefer toadd to the mixture about 10% of tungsticoxid so that when themxture is heated up in the furnace there ma beenough oxygen .present to eliminate al l,carbon and yield a refractorybody of ure tungsten. This mixture when rst m0 ded or pressed isl ratherbrittle and inclined to crumble but 'ind thatby heating itin a vacuum toabout 1390" C., l can com letely change its 'characteristics and ren erit strong and relatively tough. After this treatment it can be machinedand otherwise manipulated much like artificial raphite. Before thefurnace is ut into regular o 'eration l .consider it' a visable to heatt ese tungsten parts toatemperature considerably hi h'er than 13000V(lin order to drive ont al' vaporizable components such as unreice loe

a plurality of superimposed rings 12 of tory bushings 13.

tungsten. These parts are shown 1n F ig. B disposed in proper relationto the refractory heaters 6. Therings12 constitute a shield to prevent`dissipation of heat toward the metal walls of the chamber and toreflect radiant heat on the cruciblevlocated Within the heating space.The rings 12 may be conveniently insulated' from other parts of theapparatus by non-conductive and refrac- 'lhe crucible 14 containing thecharge to be melted may be supported on a tungsten .pedestal l5 carryinga cap 16. The pedestal 15 may be conveniently supportedby iron bars 1'?engaging with the lower brass pipe 4 and insulated therefrom. The brasspipes 4 and 5 serve not only to transmit current to and from therefractory conductors but they also serve as means for carrying acooling'liqhid through blocks 8, l0, and l1 whereby these parts aremaintained at a relatively low temperature even though the resistanceconductors are run at lan exceedingly high heat. y

To insure a good connection between the refractory heaters G and theblocks f in which they are mounted, l may use the means of connectionshown in Fig. 4. rlhe lower block is provided with a cup 18 filled withtungsten powder in which the lower end of the refractory heater isembedded.

The powder is pressed firmly in position by.

means -of a tungsten bushing.y 19 pushed down on top of the powder. ndthat such a joint becomes vvery strong after the initial operation ofthe furnace, because of sintering or similar action between theparticles of the powder whereby, the entire joint becomes relativelysolid and strong and insures a good electrical connection to therefractory heater. At the top of the 'heater the joint is similarly madeexcept that the heater enters the cup of tungsten 'powder from below. Asan alternative means of connecting the heaters I may clamp'theendsbetween tungsten blocks. y

The furnace may be waterc'ooled-'-aiid may be provided with a suitable`peep hole 21 covered with a plate of mica 22. l"

The modication shown in- Fig. 5. includes many of the features shown inFig. 1, but is provided with a tubular heater 1n place of the series ofrods heretofore described. This tubular heater 23 is clamped atthe to ina tungsten block 24 and the latter lis e ectrically connected to a U-shaed tube 25 of brass or other metal. At the ottom the refractory tube ismounted in a tungsten cup 26 and the latter is clamped between suitabletungsten blocks 27, one of which is shown in the drawings. A secondmetal tube 28 serves as a means for connecting the lower end of theheater with the electrical circuitand also serves to support vtheannular shield 29 which surrounds the heating tube and concentrates theheat within the tube.I A tungsten pedestal 30 is mounted within the tubeto serve as a support for a crucible or other article to be heated. Iprefer lto insulate this pedestal from other parts of the heater by alava bushing 31 and I prefer to insulate the tungsten shield from thesupporting clamps 32 by vsimilar bushings to decrease the tendency fordissociation of the heater or of theheated parts because of theliberation of charged particles at the enormous temperature to whichthese elements are subjected during normal operation of the furnace. If

desired, the tubular heater may be divided by a helical slot to increasethe voltage across the heater for any given current.

I find either of the modications above described to be very serviceablefor the treatment of the more refractory metals and materials and forthe production of a predetermined and controllable temperature. Thefurnace may be used for the continued heating of tungsten without dangerof contaminatingthc charge by vapors or charged particles given mi bythe heating elements of the furnace. As the entire evacuated chamber isfree from carbon, the highest temperature may be produced without dangerof contaminating the charge with carbon, or producing a carbid from thema'.-

terial under treatment.

3. vThe combination of an air-tight cham-l ber, means for continuouslyexhausting air from said chamber, and a refractory heating membermounted in said chamber and consisting of lcompressed tungsten powder.

4. ln a vacuum furnace, a heating member consisting of compressedtungsten powder, Ameans for supporting material to be heated inproximity to said heating mem- '.ber, and terminalsfor the heatingmember consisting of tungsten block"s.

5. ln a vacuum furnace, a heating space having tungsten walls', and arefractory heater therein of substantially pure tungsten. f

6. The combination of an air tight chaine bei', means for supportingmaterial to be treated in said chamber, and means out of contact withsaid material for heating it to a temperature approaching the fusingpoint of tungsten, in a space free from carbon.

7. In avacuum furnace, a resistance conductor of compressed tungstenpowder, and material to be treated placed in proximity to said heaterand receiving radiant energy therefrom.

8. A vacuum furnace of the resistance type having an incandescentconductor of substantially pure tungsten. I

9. A vacuum furnace of the resistance type having an incandescentconductor consist-ing substantially of pure -n'ietal powder sinteredinto a coherent body and having a fusing temperature as high or higherthan the temperature at which carbon appears to disintegrate. p

10. The combination of an air-tiglit chamber, means for supporting acharge of me- I tallic material therein, and a resistance conductor forheatincr said charge said conductor consisting of material the vapor ofwhich is chemically inert with respect to the charge under treatment attemperatures approaching the fusing. temperature of the more refractorymetals.

11. A furnace of the resistance type hav.- ing a furnace chamberinclosing a tubular resistance conductor of 'substantially puretungsten. y

1,2. A vacuum furnace of the resistance type having a furnace chamberinclosing a tubular resistance conductor -of substantially pure tungstenWithin which the material to be heated can be introduced.

18. The. combination of an evacuated chamber, a tungsten tube therein,means for supplying current to said tube to heat the saine, and meansfor -supporting material within said tube but out of Contact therewith.".f-

14. A tubular resistance member of pure 'tungsten having a bore largeenoughto ad mit a Crucible.

15. A tubular resistance heater of pure tungsten having a helical slot.

In Witnessl whereof, I have hereunto set my hand this 30th day of June,1906.

AXELy O. APPELBERG.

VitneSSes y .EDWARD WILLIAMS, Jr., ARBAB. MARVIN, Jr.

